With the development of flat panel display (FPD), as for achieving the curved surface display of large-sized panels pursuing vivid sense of presence, flexibility of winding type mobile terminals pursuing portability and convenience, substrates with both flexibility and impact resistance are indispensible. As for a FPD substrate, glass substrates or materials such as polyimide resin are widely used. However, a flexible substrate is easily over bent, which causes crack or damage or falling off of inner devices, and further affects characteristic and service life.